We have previously reported the design and synthesis of various dibasic fXa inhibitors using amino acids such as 3-OH-proline, m-amidinophenylalanine, and 2,3-diamino propionic acid as templates ( 1 in Fig. 1). 4 To discover novel inhibitors with improved bioavailability, we focused our synthetic efforts on reducing the overall basicity and enhancing the potency of this series of compounds. Quan et al. 5 has reported isoxazoline-containing fXa inhibitors (2 in Fig. ...